The present invention relates to a copier, printer, facsimile apparatus or similar image forming apparatus and, more particularly, to a device for storing printings, film sheets or similar recording media driven out or an image forming apparatus.
It is a common practice with, for example, a printer to provide a sheet discharging device implemented by a plurality of trays. A printer whose trays are each usable as a job separator or a mail box is conventional. Job separators refer to a function of discharging a series of printings (called a job hereinafter) while separating them from the others, while mail boxes refer to a function of allocating each tray to a particular user and distributing printings to the individual trays. The sheet discharging device has a plurality of trays arranged one above another in the same way as the trays of a sorter or stacker for a copier, as disclosed in, for example, Japanese Patent Laid-Open Publication No. 63-60870.
With a copier, it is a common practice for the operator to manipulate the copier while standing by the copier, so that sheets can be taken out of a sorter or a stacker easily. On the other hand, a printer connected to a network and capable of producing a great amount of printings is usually controlled at individual remote stations. Moreover, the printer for network use is generally shared by a great number of users, e.g., several tens to several thousands of person in a LAN (Local Area Network) or similar network environment. This kind of printer has a problem when implemented with a stack of trays of the same type as conventionally applied to the sorter or stacker of a copier. Specifically, although the trays may be used as job separators, it is difficult for a user to locate one of the trays received printings (job) which the user commanded. Should the user inadvertently take out printings meant for another user, not only printings addressed to the user would be left in the device, but also the other users would suffer damage in the secrecy aspect. Furthermore, when more than a hundred users share the printer, it is difficult to implement mail boxes, i.e., to provide the same number of trays as the number of users. In addition, providing such a great number of mail boxes is wasteful since not all the users command printing at all times, i.e., most mail boxes remain empty at all times. It is also difficult to change the number of trays. Moreover, considering the fact that the number of users sharing the same printer constantly changes, it is difficult to determine how many trays should be attached to the printer at the time of purchase. Hence, the printer suffers from a lack in expansibility and flexibility.